Sink waste to strap boss fail. Solutions welcome...!

[PoundofCarrots]

Good Morning. The boss insert to the strap on the soil pipe has come out as it looks as though the weld has failed and the sink waste is leaking onto the patio below. The pipe is welded at both ends so I can't remove it to replace weld in a new boss. It appears as though the only solution might be to cut the pipe in the middle, pull the pipe and boss end out of the soil pipe and join a new piece of pipe where the cut is made. I hope this makes sense and if anybody has a better (easier!) solution, then I'd be grateful.

Thanks in advance.

 

[denso13]

cut the pipe in the middle, pull the pipe and boss end out of the soil pipe and join a new piece of pipe where the cut is made

Sounds good. Finding the correct boss/rubber for the existing one might be the problem.

 

[PoundofCarrots]

Ah, I was hoping it might just be a standard size replacement...

 

[Madrab]

I may be wrong but that already looks like a push fit rubber boss reducer, not a glued reducer, it should just push back in.

or if enough give in the pipe, take off, clean it up fitting and reducer then refit with a little silicone adhesive (not sealant).

If not enough play in the pipe then cutting anywhere and redo the boss fitting and then re-couple is the other option. You could replace the rubber reducer with a push fit solvent weld type if the fall isn't too great

 

[denso13]

Something like this might do, but they aren't universal unfortunately, https://www.toolstation.com/boss-rubber-adaptor/p37469

 

[PoundofCarrots]

Thank you for the replies. Here are a couple more photos of the boss. I'm not sure if the gloopy residue is the old glue or something else?!

 

[Madrab]

Definitely an old rubber reducer, the goo may be an old acrylic silicone or TBH it actually looks like it could be soaked toilet paper from the toilet outflow above.

You need to get that cleaned and sealed back in/renewed as it may not be sink outflow rather effluent from the toilet, as it's just at the right spot to catch the waste, that's ending up on your patio. You could push it back in and use a tie wrap to hold it in temporarily until it fixed properly

 

[PoundofCarrots]

Thanks Rob. I fear you are right. Struggling to get it to go back in fully and trying with a couple of clamps. When you say 'fixed properly', do you think a solvent weld as you suggested above would be the best solution?

 

[Madrab]

do you think a solvent weld as you suggested above would be the best solution

Always use solvent weld where possible, done properly it's a pretty permanent fix, more so due to where it is located just at the fall spot from the toilet outflow. The fitter should have thought about outflow/crossflow from the toilet, as where it is it would always put that connection under a bit more pressure than normal. Don't worry about the adapter fit, it's not meant to go all the way in, the last part of the adapter should sit proud of the boss so doesn't need to be held that tightly

If you can get up an measure the outside diameter of the boss, hopefully it will be ~63mm, if so then get a solvent weld connector and dry fit to ensure the fall on the waste pipe isn't too great to allow it to fit properly, though looking at it, it should be ok, then glue it all together. If not then there are other alternatives that can be installed.

 

[PoundofCarrots]

Thank you. My callipers are saying nearer to 68mm but it's probably just the point I'm measuring at. Because I can't get the old boss to push in fully, I'm now thinking of going back to the original plan of sawing the pipe and removing the whole thing including the strap and refitting with a piece of pipe coupled to the old piece.

 

[Madrab]

Sorry - Typo - should be internal diameter should be around 63mm.
FYI the strap boss is the component that is glued to the down pipe with the strap around it. The boss adapter is the rubber finned component that holds the waste pipe into the fitting.

You should be able to keep the strap boss and then either use a solvent weld (32mm/40mm) adapter in the boss or a new (32mm/40mm) rubber adapter with a little silicone adhesive.

Also as suggested, the whole rubber adapter doesn't fit inside the boss, just up to the last/larger fin, as per the previous pic.

 

[PoundofCarrots]

I cut the pipe and went to the plumbing merchant and bought a new strap boss and adapter (solvent fit not rubber). Unfortunately, it doesn't fit the size of the existing hole in the soil pipe. I did query this at the merchant but they said just use a file to enlarge the hole!

It's quite difficult to increase the hole evenly by 3mm I think so I'm kind of back to using the existing strap boss as the new Floplast insert doesn't fit the old strap boss! If I could just enlarge the hole in the soil pipe, I could move on! Thanks again anyway.

 

[PoundofCarrots]

These photos show the fit of the new solvent adapter in the old boss vs the fit in the new boss.

 

[denso13]

It's quite difficult to increase the hole evenly by 3mm

Being plastic is shouldn't be too difficult. A nice hot (old) knife can help.

Definitely fit the new one if you can.

 

[Madrab]

If the old one came off that easily then yep, fit the new one if you can. The strap on boss would usually be glued onto the stack too as well as the strap, I presume you got some solvent cement too? Roughen up the joining surfaces to take the shine off before gluing. If you have a junior hacksaw blade then run round slowly with that.

TBH tho, that adapter's fit into the old boss isn't too bad, especially once it's glued in, it's obviously a few mm longer than needed so would probably fit fine once the back's sanded down with some 80grit on a flat surface.